/*
 * jmemmgr.c
 *
 * Copyright (C) 1991-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the JPEG system-independent memory management
 * routines.  This code is usable across a wide variety of machines; most
 * of the system dependencies have been isolated in a separate file.
 * The major functions provided here are:
 *   * pool-based allocation and freeing of memory;
 *   * policy decisions about how to divide available memory among the
 *     virtual arrays;
 *   * control logic for swapping virtual arrays between main memory and
 *     backing storage.
 * The separate system-dependent file provides the actual backing-storage
 * access code, and it contains the policy decision about how much total
 * main memory to use.
 * This file is system-dependent in the sense that some of its functions
 * are unnecessary in some systems.  For example, if there is enough virtual
 * memory so that backing storage will never be used, much of the virtual
 * array control logic could be removed.  (Of course, if you have that much
 * memory then you shouldn't care about a little bit of unused code...)
 */

#define JPEG_INTERNALS
#define AM_MEMORY_MANAGER		/* we define jvirt_Xarray_control structs */
#include "jinclude.h"
#include "jpeglib.h"
#include "jmemsys.h"			/* import the system-dependent declarations */

#ifndef NO_GETENV
#ifndef HAVE_STDLIB_H			/* <stdlib.h> should declare getenv() */
extern char    *getenv JPP((const char *name));
#endif
#endif


/*
 * Some important notes:
 *   The allocation routines provided here must never return NULL.
 *   They should exit to error_exit if unsuccessful.
 *
 *   It's not a good idea to try to merge the sarray and barray routines,
 *   even though they are textually almost the same, because samples are
 *   usually stored as bytes while coefficients are shorts or ints.  Thus,
 *   in machines where byte pointers have a different representation from
 *   word pointers, the resulting machine code could not be the same.
 */


/*
 * Many machines require storage alignment: longs must start on 4-byte
 * boundaries, doubles on 8-byte boundaries, etc.  On such machines, malloc()
 * always returns pointers that are multiples of the worst-case alignment
 * requirement, and we had better do so too.
 * There isn't any really portable way to determine the worst-case alignment
 * requirement.  This module assumes that the alignment requirement is
 * multiples of sizeof(ALIGN_TYPE).
 * By default, we define ALIGN_TYPE as double.  This is necessary on some
 * workstations (where doubles really do need 8-byte alignment) and will work
 * fine on nearly everything.  If your machine has lesser alignment needs,
 * you can save a few bytes by making ALIGN_TYPE smaller.
 * The only place I know of where this will NOT work is certain Macintosh
 * 680x0 compilers that define double as a 10-byte IEEE extended float.
 * Doing 10-byte alignment is counterproductive because longwords won't be
 * aligned well.  Put "#define ALIGN_TYPE long" in jconfig.h if you have
 * such a compiler.
 */

#ifndef ALIGN_TYPE				/* so can override from jconfig.h */
#define ALIGN_TYPE  double
#endif


/*
 * We allocate objects from "pools", where each pool is gotten with a single
 * request to jpeg_get_small() or jpeg_get_large().  There is no per-object
 * overhead within a pool, except for alignment padding.  Each pool has a
 * header with a link to the next pool of the same class.
 * Small and large pool headers are identical except that the latter's
 * link pointer must be FAR on 80x86 machines.
 * Notice that the "real" header fields are union'ed with a dummy ALIGN_TYPE
 * field.  This forces the compiler to make SIZEOF(small_pool_hdr) a multiple
 * of the alignment requirement of ALIGN_TYPE.
 */

typedef union small_pool_struct *small_pool_ptr;

typedef union small_pool_struct
{
	struct
	{
		small_pool_ptr  next;	/* next in list of pools */
		size_t          bytes_used;	/* how many bytes already used within pool */
		size_t          bytes_left;	/* bytes still available in this pool */
	} hdr;
	ALIGN_TYPE      dummy;		/* included in union to ensure alignment */
} small_pool_hdr;

typedef union large_pool_struct FAR *large_pool_ptr;

typedef union large_pool_struct
{
	struct
	{
		large_pool_ptr  next;	/* next in list of pools */
		size_t          bytes_used;	/* how many bytes already used within pool */
		size_t          bytes_left;	/* bytes still available in this pool */
	} hdr;
	ALIGN_TYPE      dummy;		/* included in union to ensure alignment */
} large_pool_hdr;


/*
 * Here is the full definition of a memory manager object.
 */

typedef struct
{
	struct jpeg_memory_mgr pub;	/* public fields */

	/* Each pool identifier (lifetime class) names a linked list of pools. */
	small_pool_ptr  small_list[JPOOL_NUMPOOLS];
	large_pool_ptr  large_list[JPOOL_NUMPOOLS];

	/* Since we only have one lifetime class of virtual arrays, only one
	 * linked list is necessary (for each datatype).  Note that the virtual
	 * array control blocks being linked together are actually stored somewhere
	 * in the small-pool list.
	 */
	jvirt_sarray_ptr virt_sarray_list;
	jvirt_barray_ptr virt_barray_list;

	/* This counts total space obtained from jpeg_get_small/large */
	long            total_space_allocated;

	/* alloc_sarray and alloc_barray set this value for use by virtual
	 * array routines.
	 */
	JDIMENSION      last_rowsperchunk;	/* from most recent alloc_sarray/barray */
} my_memory_mgr;

typedef my_memory_mgr *my_mem_ptr;


/*
 * The control blocks for virtual arrays.
 * Note that these blocks are allocated in the "small" pool area.
 * System-dependent info for the associated backing store (if any) is hidden
 * inside the backing_store_info struct.
 */

struct jvirt_sarray_control
{
	JSAMPARRAY      mem_buffer;	/* => the in-memory buffer */
	JDIMENSION      rows_in_array;	/* total virtual array height */
	JDIMENSION      samplesperrow;	/* width of array (and of memory buffer) */
	JDIMENSION      maxaccess;	/* max rows accessed by access_virt_sarray */
	JDIMENSION      rows_in_mem;	/* height of memory buffer */
	JDIMENSION      rowsperchunk;	/* allocation chunk size in mem_buffer */
	JDIMENSION      cur_start_row;	/* first logical row # in the buffer */
	JDIMENSION      first_undef_row;	/* row # of first uninitialized row */
	boolean         pre_zero;	/* pre-zero mode requested? */
	boolean         dirty;		/* do current buffer contents need written? */
	boolean         b_s_open;	/* is backing-store data valid? */
	jvirt_sarray_ptr next;		/* link to next virtual sarray control block */
	backing_store_info b_s_info;	/* System-dependent control info */
};

struct jvirt_barray_control
{
	JBLOCKARRAY     mem_buffer;	/* => the in-memory buffer */
	JDIMENSION      rows_in_array;	/* total virtual array height */
	JDIMENSION      blocksperrow;	/* width of array (and of memory buffer) */
	JDIMENSION      maxaccess;	/* max rows accessed by access_virt_barray */
	JDIMENSION      rows_in_mem;	/* height of memory buffer */
	JDIMENSION      rowsperchunk;	/* allocation chunk size in mem_buffer */
	JDIMENSION      cur_start_row;	/* first logical row # in the buffer */
	JDIMENSION      first_undef_row;	/* row # of first uninitialized row */
	boolean         pre_zero;	/* pre-zero mode requested? */
	boolean         dirty;		/* do current buffer contents need written? */
	boolean         b_s_open;	/* is backing-store data valid? */
	jvirt_barray_ptr next;		/* link to next virtual barray control block */
	backing_store_info b_s_info;	/* System-dependent control info */
};


#ifdef MEM_STATS				/* optional extra stuff for statistics */

LOCAL void print_mem_stats(j_common_ptr cinfo, int pool_id)
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	small_pool_ptr  shdr_ptr;
	large_pool_ptr  lhdr_ptr;

	/* Since this is only a debugging stub, we can cheat a little by using
	 * fprintf directly rather than going through the trace message code.
	 * This is helpful because message parm array can't handle longs.
	 */
	fprintf(stderr, "Freeing pool %d, total space = %ld\n", pool_id, mem->total_space_allocated);

	for(lhdr_ptr = mem->large_list[pool_id]; lhdr_ptr != NULL; lhdr_ptr = lhdr_ptr->hdr.next)
	{
		fprintf(stderr, "  Large chunk used %ld\n", (long)lhdr_ptr->hdr.bytes_used);
	}

	for(shdr_ptr = mem->small_list[pool_id]; shdr_ptr != NULL; shdr_ptr = shdr_ptr->hdr.next)
	{
		fprintf(stderr, "  Small chunk used %ld free %ld\n", (long)shdr_ptr->hdr.bytes_used, (long)shdr_ptr->hdr.bytes_left);
	}
}

#endif							/* MEM_STATS */


LOCAL void out_of_memory(j_common_ptr cinfo, int which)
/* Report an out-of-memory error and stop execution */
/* If we compiled MEM_STATS support, report alloc requests before dying */
{
#ifdef MEM_STATS
	cinfo->err->trace_level = 2;	/* force self_destruct to report stats */
#endif
	ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, which);
}


/*
 * Allocation of "small" objects.
 *
 * For these, we use pooled storage.  When a new pool must be created,
 * we try to get enough space for the current request plus a "slop" factor,
 * where the slop will be the amount of leftover space in the new pool.
 * The speed vs. space tradeoff is largely determined by the slop values.
 * A different slop value is provided for each pool class (lifetime),
 * and we also distinguish the first pool of a class from later ones.
 * NOTE: the values given work fairly well on both 16- and 32-bit-int
 * machines, but may be too small if longs are 64 bits or more.
 */

static const size_t first_pool_slop[JPOOL_NUMPOOLS] = {
	1600,						/* first PERMANENT pool */
	16000						/* first IMAGE pool */
};

static const size_t extra_pool_slop[JPOOL_NUMPOOLS] = {
	0,							/* additional PERMANENT pools */
	5000						/* additional IMAGE pools */
};

#define MIN_SLOP  50			/* greater than 0 to avoid futile looping */


METHODDEF void *alloc_small(j_common_ptr cinfo, int pool_id, size_t sizeofobject)
/* Allocate a "small" object */
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	small_pool_ptr  hdr_ptr, prev_hdr_ptr;
	char           *data_ptr;
	size_t          odd_bytes, min_request, slop;

	/* Check for unsatisfiable request (do now to ensure no overflow below) */
	if(sizeofobject > (size_t) (MAX_ALLOC_CHUNK - SIZEOF(small_pool_hdr)))
		out_of_memory(cinfo, 1);	/* request exceeds malloc's ability */

	/* Round up the requested size to a multiple of SIZEOF(ALIGN_TYPE) */
	odd_bytes = sizeofobject % SIZEOF(ALIGN_TYPE);
	if(odd_bytes > 0)
		sizeofobject += SIZEOF(ALIGN_TYPE) - odd_bytes;

	/* See if space is available in any existing pool */
	if(pool_id < 0 || pool_id >= JPOOL_NUMPOOLS)
		ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */
	prev_hdr_ptr = NULL;
	hdr_ptr = mem->small_list[pool_id];
	while(hdr_ptr != NULL)
	{
		if(hdr_ptr->hdr.bytes_left >= sizeofobject)
			break;				/* found pool with enough space */
		prev_hdr_ptr = hdr_ptr;
		hdr_ptr = hdr_ptr->hdr.next;
	}

	/* Time to make a new pool? */
	if(hdr_ptr == NULL)
	{
		/* min_request is what we need now, slop is what will be leftover */
		min_request = sizeofobject + SIZEOF(small_pool_hdr);
		if(prev_hdr_ptr == NULL)	/* first pool in class? */
			slop = first_pool_slop[pool_id];
		else
			slop = extra_pool_slop[pool_id];
		/* Don't ask for more than MAX_ALLOC_CHUNK */
		if(slop > (size_t) (MAX_ALLOC_CHUNK - min_request))
			slop = (size_t) (MAX_ALLOC_CHUNK - min_request);
		/* Try to get space, if fail reduce slop and try again */
		for(;;)
		{
			hdr_ptr = (small_pool_ptr) jpeg_get_small(cinfo, min_request + slop);
			if(hdr_ptr != NULL)
				break;
			slop /= 2;
			if(slop < MIN_SLOP)	/* give up when it gets real small */
				out_of_memory(cinfo, 2);	/* jpeg_get_small failed */
		}
		mem->total_space_allocated += min_request + slop;
		/* Success, initialize the new pool header and add to end of list */
		hdr_ptr->hdr.next = NULL;
		hdr_ptr->hdr.bytes_used = 0;
		hdr_ptr->hdr.bytes_left = sizeofobject + slop;
		if(prev_hdr_ptr == NULL)	/* first pool in class? */
			mem->small_list[pool_id] = hdr_ptr;
		else
			prev_hdr_ptr->hdr.next = hdr_ptr;
	}

	/* OK, allocate the object from the current pool */
	data_ptr = (char *)(hdr_ptr + 1);	/* point to first data byte in pool */
	data_ptr += hdr_ptr->hdr.bytes_used;	/* point to place for object */
	hdr_ptr->hdr.bytes_used += sizeofobject;
	hdr_ptr->hdr.bytes_left -= sizeofobject;

	return (void *)data_ptr;
}


/*
 * Allocation of "large" objects.
 *
 * The external semantics of these are the same as "small" objects,
 * except that FAR pointers are used on 80x86.  However the pool
 * management heuristics are quite different.  We assume that each
 * request is large enough that it may as well be passed directly to
 * jpeg_get_large; the pool management just links everything together
 * so that we can free it all on demand.
 * Note: the major use of "large" objects is in JSAMPARRAY and JBLOCKARRAY
 * structures.  The routines that create these structures (see below)
 * deliberately bunch rows together to ensure a large request size.
 */

METHODDEF void FAR *alloc_large(j_common_ptr cinfo, int pool_id, size_t sizeofobject)
/* Allocate a "large" object */
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	large_pool_ptr  hdr_ptr;
	size_t          odd_bytes;

	/* Check for unsatisfiable request (do now to ensure no overflow below) */
	if(sizeofobject > (size_t) (MAX_ALLOC_CHUNK - SIZEOF(large_pool_hdr)))
		out_of_memory(cinfo, 3);	/* request exceeds malloc's ability */

	/* Round up the requested size to a multiple of SIZEOF(ALIGN_TYPE) */
	odd_bytes = sizeofobject % SIZEOF(ALIGN_TYPE);
	if(odd_bytes > 0)
		sizeofobject += SIZEOF(ALIGN_TYPE) - odd_bytes;

	/* Always make a new pool */
	if(pool_id < 0 || pool_id >= JPOOL_NUMPOOLS)
		ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */

	hdr_ptr = (large_pool_ptr) jpeg_get_large(cinfo, sizeofobject + SIZEOF(large_pool_hdr));
	if(hdr_ptr == NULL)
		out_of_memory(cinfo, 4);	/* jpeg_get_large failed */
	mem->total_space_allocated += sizeofobject + SIZEOF(large_pool_hdr);

	/* Success, initialize the new pool header and add to list */
	hdr_ptr->hdr.next = mem->large_list[pool_id];
	/* We maintain space counts in each pool header for statistical purposes,
	 * even though they are not needed for allocation.
	 */
	hdr_ptr->hdr.bytes_used = sizeofobject;
	hdr_ptr->hdr.bytes_left = 0;
	mem->large_list[pool_id] = hdr_ptr;

	return (void FAR *)(hdr_ptr + 1);	/* point to first data byte in pool */
}


/*
 * Creation of 2-D sample arrays.
 * The pointers are in near heap, the samples themselves in FAR heap.
 *
 * To minimize allocation overhead and to allow I/O of large contiguous
 * blocks, we allocate the sample rows in groups of as many rows as possible
 * without exceeding MAX_ALLOC_CHUNK total bytes per allocation request.
 * NB: the virtual array control routines, later in this file, know about
 * this chunking of rows.  The rowsperchunk value is left in the mem manager
 * object so that it can be saved away if this sarray is the workspace for
 * a virtual array.
 */

METHODDEF       JSAMPARRAY alloc_sarray(j_common_ptr cinfo, int pool_id, JDIMENSION samplesperrow, JDIMENSION numrows)
/* Allocate a 2-D sample array */
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	JSAMPARRAY      result;
	JSAMPROW        workspace;
	JDIMENSION      rowsperchunk, currow, i;
	long            ltemp;

	/* Calculate max # of rows allowed in one allocation chunk */
	ltemp = (MAX_ALLOC_CHUNK - SIZEOF(large_pool_hdr)) / ((long)samplesperrow * SIZEOF(JSAMPLE));
	if(ltemp <= 0)
		ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
	if(ltemp < (long)numrows)
		rowsperchunk = (JDIMENSION) ltemp;
	else
		rowsperchunk = numrows;
	mem->last_rowsperchunk = rowsperchunk;

	/* Get space for row pointers (small object) */
	result = (JSAMPARRAY) alloc_small(cinfo, pool_id, (size_t) (numrows * SIZEOF(JSAMPROW)));

	/* Get the rows themselves (large objects) */
	currow = 0;
	while(currow < numrows)
	{
		rowsperchunk = MIN(rowsperchunk, numrows - currow);
		workspace = (JSAMPROW) alloc_large(cinfo, pool_id,
										   (size_t) ((size_t) rowsperchunk * (size_t) samplesperrow * SIZEOF(JSAMPLE)));
		for(i = rowsperchunk; i > 0; i--)
		{
			result[currow++] = workspace;
			workspace += samplesperrow;
		}
	}

	return result;
}


/*
 * Creation of 2-D coefficient-block arrays.
 * This is essentially the same as the code for sample arrays, above.
 */

METHODDEF       JBLOCKARRAY alloc_barray(j_common_ptr cinfo, int pool_id, JDIMENSION blocksperrow, JDIMENSION numrows)
/* Allocate a 2-D coefficient-block array */
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	JBLOCKARRAY     result;
	JBLOCKROW       workspace;
	JDIMENSION      rowsperchunk, currow, i;
	long            ltemp;

	/* Calculate max # of rows allowed in one allocation chunk */
	ltemp = (MAX_ALLOC_CHUNK - SIZEOF(large_pool_hdr)) / ((long)blocksperrow * SIZEOF(JBLOCK));
	if(ltemp <= 0)
		ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
	if(ltemp < (long)numrows)
		rowsperchunk = (JDIMENSION) ltemp;
	else
		rowsperchunk = numrows;
	mem->last_rowsperchunk = rowsperchunk;

	/* Get space for row pointers (small object) */
	result = (JBLOCKARRAY) alloc_small(cinfo, pool_id, (size_t) (numrows * SIZEOF(JBLOCKROW)));

	/* Get the rows themselves (large objects) */
	currow = 0;
	while(currow < numrows)
	{
		rowsperchunk = MIN(rowsperchunk, numrows - currow);
		workspace = (JBLOCKROW) alloc_large(cinfo, pool_id,
											(size_t) ((size_t) rowsperchunk * (size_t) blocksperrow * SIZEOF(JBLOCK)));
		for(i = rowsperchunk; i > 0; i--)
		{
			result[currow++] = workspace;
			workspace += blocksperrow;
		}
	}

	return result;
}


/*
 * About virtual array management:
 *
 * The above "normal" array routines are only used to allocate strip buffers
 * (as wide as the image, but just a few rows high).  Full-image-sized buffers
 * are handled as "virtual" arrays.  The array is still accessed a strip at a
 * time, but the memory manager must save the whole array for repeated
 * accesses.  The intended implementation is that there is a strip buffer in
 * memory (as high as is possible given the desired memory limit), plus a
 * backing file that holds the rest of the array.
 *
 * The request_virt_array routines are told the total size of the image and
 * the maximum number of rows that will be accessed at once.  The in-memory
 * buffer must be at least as large as the maxaccess value.
 *
 * The request routines create control blocks but not the in-memory buffers.
 * That is postponed until realize_virt_arrays is called.  At that time the
 * total amount of space needed is known (approximately, anyway), so free
 * memory can be divided up fairly.
 *
 * The access_virt_array routines are responsible for making a specific strip
 * area accessible (after reading or writing the backing file, if necessary).
 * Note that the access routines are told whether the caller intends to modify
 * the accessed strip; during a read-only pass this saves having to rewrite
 * data to disk.  The access routines are also responsible for pre-zeroing
 * any newly accessed rows, if pre-zeroing was requested.
 *
 * In current usage, the access requests are usually for nonoverlapping
 * strips; that is, successive access start_row numbers differ by exactly
 * num_rows = maxaccess.  This means we can get good performance with simple
 * buffer dump/reload logic, by making the in-memory buffer be a multiple
 * of the access height; then there will never be accesses across bufferload
 * boundaries.  The code will still work with overlapping access requests,
 * but it doesn't handle bufferload overlaps very efficiently.
 */


METHODDEF       jvirt_sarray_ptr
request_virt_sarray(j_common_ptr cinfo, int pool_id, boolean pre_zero,
					JDIMENSION samplesperrow, JDIMENSION numrows, JDIMENSION maxaccess)
/* Request a virtual 2-D sample array */
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	jvirt_sarray_ptr result;

	/* Only IMAGE-lifetime virtual arrays are currently supported */
	if(pool_id != JPOOL_IMAGE)
		ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */

	/* get control block */
	result = (jvirt_sarray_ptr) alloc_small(cinfo, pool_id, SIZEOF(struct jvirt_sarray_control));

	result->mem_buffer = NULL;	/* marks array not yet realized */
	result->rows_in_array = numrows;
	result->samplesperrow = samplesperrow;
	result->maxaccess = maxaccess;
	result->pre_zero = pre_zero;
	result->b_s_open = FALSE;	/* no associated backing-store object */
	result->next = mem->virt_sarray_list;	/* add to list of virtual arrays */
	mem->virt_sarray_list = result;

	return result;
}


METHODDEF       jvirt_barray_ptr
request_virt_barray(j_common_ptr cinfo, int pool_id, boolean pre_zero,
					JDIMENSION blocksperrow, JDIMENSION numrows, JDIMENSION maxaccess)
/* Request a virtual 2-D coefficient-block array */
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	jvirt_barray_ptr result;

	/* Only IMAGE-lifetime virtual arrays are currently supported */
	if(pool_id != JPOOL_IMAGE)
		ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */

	/* get control block */
	result = (jvirt_barray_ptr) alloc_small(cinfo, pool_id, SIZEOF(struct jvirt_barray_control));

	result->mem_buffer = NULL;	/* marks array not yet realized */
	result->rows_in_array = numrows;
	result->blocksperrow = blocksperrow;
	result->maxaccess = maxaccess;
	result->pre_zero = pre_zero;
	result->b_s_open = FALSE;	/* no associated backing-store object */
	result->next = mem->virt_barray_list;	/* add to list of virtual arrays */
	mem->virt_barray_list = result;

	return result;
}


METHODDEF void realize_virt_arrays(j_common_ptr cinfo)
/* Allocate the in-memory buffers for any unrealized virtual arrays */
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	long            space_per_minheight, maximum_space, avail_mem;
	long            minheights, max_minheights;
	jvirt_sarray_ptr sptr;
	jvirt_barray_ptr bptr;

	/* Compute the minimum space needed (maxaccess rows in each buffer)
	 * and the maximum space needed (full image height in each buffer).
	 * These may be of use to the system-dependent jpeg_mem_available routine.
	 */
	space_per_minheight = 0;
	maximum_space = 0;
	for(sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next)
	{
		if(sptr->mem_buffer == NULL)
		{						/* if not realized yet */
			space_per_minheight += (long)sptr->maxaccess * (long)sptr->samplesperrow * SIZEOF(JSAMPLE);
			maximum_space += (long)sptr->rows_in_array * (long)sptr->samplesperrow * SIZEOF(JSAMPLE);
		}
	}
	for(bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next)
	{
		if(bptr->mem_buffer == NULL)
		{						/* if not realized yet */
			space_per_minheight += (long)bptr->maxaccess * (long)bptr->blocksperrow * SIZEOF(JBLOCK);
			maximum_space += (long)bptr->rows_in_array * (long)bptr->blocksperrow * SIZEOF(JBLOCK);
		}
	}

	if(space_per_minheight <= 0)
		return;					/* no unrealized arrays, no work */

	/* Determine amount of memory to actually use; this is system-dependent. */
	avail_mem = jpeg_mem_available(cinfo, space_per_minheight, maximum_space, mem->total_space_allocated);

	/* If the maximum space needed is available, make all the buffers full
	 * height; otherwise parcel it out with the same number of minheights
	 * in each buffer.
	 */
	if(avail_mem >= maximum_space)
		max_minheights = 1000000000L;
	else
	{
		max_minheights = avail_mem / space_per_minheight;
		/* If there doesn't seem to be enough space, try to get the minimum
		 * anyway.  This allows a "stub" implementation of jpeg_mem_available().
		 */
		if(max_minheights <= 0)
			max_minheights = 1;
	}

	/* Allocate the in-memory buffers and initialize backing store as needed. */

	for(sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next)
	{
		if(sptr->mem_buffer == NULL)
		{						/* if not realized yet */
			minheights = ((long)sptr->rows_in_array - 1L) / sptr->maxaccess + 1L;
			if(minheights <= max_minheights)
			{
				/* This buffer fits in memory */
				sptr->rows_in_mem = sptr->rows_in_array;
			}
			else
			{
				/* It doesn't fit in memory, create backing store. */
				sptr->rows_in_mem = (JDIMENSION) (max_minheights * sptr->maxaccess);
				jpeg_open_backing_store(cinfo, &sptr->b_s_info,
										(long)sptr->rows_in_array * (long)sptr->samplesperrow * (long)SIZEOF(JSAMPLE));
				sptr->b_s_open = TRUE;
			}
			sptr->mem_buffer = alloc_sarray(cinfo, JPOOL_IMAGE, sptr->samplesperrow, sptr->rows_in_mem);
			sptr->rowsperchunk = mem->last_rowsperchunk;
			sptr->cur_start_row = 0;
			sptr->first_undef_row = 0;
			sptr->dirty = FALSE;
		}
	}

	for(bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next)
	{
		if(bptr->mem_buffer == NULL)
		{						/* if not realized yet */
			minheights = ((long)bptr->rows_in_array - 1L) / bptr->maxaccess + 1L;
			if(minheights <= max_minheights)
			{
				/* This buffer fits in memory */
				bptr->rows_in_mem = bptr->rows_in_array;
			}
			else
			{
				/* It doesn't fit in memory, create backing store. */
				bptr->rows_in_mem = (JDIMENSION) (max_minheights * bptr->maxaccess);
				jpeg_open_backing_store(cinfo, &bptr->b_s_info,
										(long)bptr->rows_in_array * (long)bptr->blocksperrow * (long)SIZEOF(JBLOCK));
				bptr->b_s_open = TRUE;
			}
			bptr->mem_buffer = alloc_barray(cinfo, JPOOL_IMAGE, bptr->blocksperrow, bptr->rows_in_mem);
			bptr->rowsperchunk = mem->last_rowsperchunk;
			bptr->cur_start_row = 0;
			bptr->first_undef_row = 0;
			bptr->dirty = FALSE;
		}
	}
}


LOCAL void do_sarray_io(j_common_ptr cinfo, jvirt_sarray_ptr ptr, boolean writing)
/* Do backing store read or write of a virtual sample array */
{
	long            bytesperrow, file_offset, byte_count, rows, thisrow, i;

	bytesperrow = (long)ptr->samplesperrow * SIZEOF(JSAMPLE);
	file_offset = ptr->cur_start_row * bytesperrow;
	/* Loop to read or write each allocation chunk in mem_buffer */
	for(i = 0; i < (long)ptr->rows_in_mem; i += ptr->rowsperchunk)
	{
		/* One chunk, but check for short chunk at end of buffer */
		rows = MIN((long)ptr->rowsperchunk, (long)ptr->rows_in_mem - i);
		/* Transfer no more than is currently defined */
		thisrow = (long)ptr->cur_start_row + i;
		rows = MIN(rows, (long)ptr->first_undef_row - thisrow);
		/* Transfer no more than fits in file */
		rows = MIN(rows, (long)ptr->rows_in_array - thisrow);
		if(rows <= 0)			/* this chunk might be past end of file! */
			break;
		byte_count = rows * bytesperrow;
		if(writing)
			(*ptr->b_s_info.write_backing_store) (cinfo, &ptr->b_s_info, (void FAR *)ptr->mem_buffer[i], file_offset, byte_count);
		else
			(*ptr->b_s_info.read_backing_store) (cinfo, &ptr->b_s_info, (void FAR *)ptr->mem_buffer[i], file_offset, byte_count);
		file_offset += byte_count;
	}
}


LOCAL void do_barray_io(j_common_ptr cinfo, jvirt_barray_ptr ptr, boolean writing)
/* Do backing store read or write of a virtual coefficient-block array */
{
	long            bytesperrow, file_offset, byte_count, rows, thisrow, i;

	bytesperrow = (long)ptr->blocksperrow * SIZEOF(JBLOCK);
	file_offset = ptr->cur_start_row * bytesperrow;
	/* Loop to read or write each allocation chunk in mem_buffer */
	for(i = 0; i < (long)ptr->rows_in_mem; i += ptr->rowsperchunk)
	{
		/* One chunk, but check for short chunk at end of buffer */
		rows = MIN((long)ptr->rowsperchunk, (long)ptr->rows_in_mem - i);
		/* Transfer no more than is currently defined */
		thisrow = (long)ptr->cur_start_row + i;
		rows = MIN(rows, (long)ptr->first_undef_row - thisrow);
		/* Transfer no more than fits in file */
		rows = MIN(rows, (long)ptr->rows_in_array - thisrow);
		if(rows <= 0)			/* this chunk might be past end of file! */
			break;
		byte_count = rows * bytesperrow;
		if(writing)
			(*ptr->b_s_info.write_backing_store) (cinfo, &ptr->b_s_info, (void FAR *)ptr->mem_buffer[i], file_offset, byte_count);
		else
			(*ptr->b_s_info.read_backing_store) (cinfo, &ptr->b_s_info, (void FAR *)ptr->mem_buffer[i], file_offset, byte_count);
		file_offset += byte_count;
	}
}


METHODDEF       JSAMPARRAY
access_virt_sarray(j_common_ptr cinfo, jvirt_sarray_ptr ptr, JDIMENSION start_row, JDIMENSION num_rows, boolean writable)
/* Access the part of a virtual sample array starting at start_row */
/* and extending for num_rows rows.  writable is true if  */
/* caller intends to modify the accessed area. */
{
	JDIMENSION      end_row = start_row + num_rows;
	JDIMENSION      undef_row;

	/* debugging check */
	if(end_row > ptr->rows_in_array || num_rows > ptr->maxaccess || ptr->mem_buffer == NULL)
		ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);

	/* Make the desired part of the virtual array accessible */
	if(start_row < ptr->cur_start_row || end_row > ptr->cur_start_row + ptr->rows_in_mem)
	{
		if(!ptr->b_s_open)
			ERREXIT(cinfo, JERR_VIRTUAL_BUG);
		/* Flush old buffer contents if necessary */
		if(ptr->dirty)
		{
			do_sarray_io(cinfo, ptr, TRUE);
			ptr->dirty = FALSE;
		}
		/* Decide what part of virtual array to access.
		 * Algorithm: if target address > current window, assume forward scan,
		 * load starting at target address.  If target address < current window,
		 * assume backward scan, load so that target area is top of window.
		 * Note that when switching from forward write to forward read, will have
		 * start_row = 0, so the limiting case applies and we load from 0 anyway.
		 */
		if(start_row > ptr->cur_start_row)
		{
			ptr->cur_start_row = start_row;
		}
		else
		{
			/* use long arithmetic here to avoid overflow & unsigned problems */
			long            ltemp;

			ltemp = (long)end_row - (long)ptr->rows_in_mem;
			if(ltemp < 0)
				ltemp = 0;		/* don't fall off front end of file */
			ptr->cur_start_row = (JDIMENSION) ltemp;
		}
		/* Read in the selected part of the array.
		 * During the initial write pass, we will do no actual read
		 * because the selected part is all undefined.
		 */
		do_sarray_io(cinfo, ptr, FALSE);
	}
	/* Ensure the accessed part of the array is defined; prezero if needed.
	 * To improve locality of access, we only prezero the part of the array
	 * that the caller is about to access, not the entire in-memory array.
	 */
	if(ptr->first_undef_row < end_row)
	{
		if(ptr->first_undef_row < start_row)
		{
			if(writable)		/* writer skipped over a section of array */
				ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
			undef_row = start_row;	/* but reader is allowed to read ahead */
		}
		else
		{
			undef_row = ptr->first_undef_row;
		}
		if(writable)
			ptr->first_undef_row = end_row;
		if(ptr->pre_zero)
		{
			size_t          bytesperrow = (size_t) ptr->samplesperrow * SIZEOF(JSAMPLE);

			undef_row -= ptr->cur_start_row;	/* make indexes relative to buffer */
			end_row -= ptr->cur_start_row;
			while(undef_row < end_row)
			{
				jzero_far((void FAR *)ptr->mem_buffer[undef_row], bytesperrow);
				undef_row++;
			}
		}
		else
		{
			if(!writable)		/* reader looking at undefined data */
				ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
		}
	}
	/* Flag the buffer dirty if caller will write in it */
	if(writable)
		ptr->dirty = TRUE;
	/* Return address of proper part of the buffer */
	return ptr->mem_buffer + (start_row - ptr->cur_start_row);
}


METHODDEF       JBLOCKARRAY
access_virt_barray(j_common_ptr cinfo, jvirt_barray_ptr ptr, JDIMENSION start_row, JDIMENSION num_rows, boolean writable)
/* Access the part of a virtual block array starting at start_row */
/* and extending for num_rows rows.  writable is true if  */
/* caller intends to modify the accessed area. */
{
	JDIMENSION      end_row = start_row + num_rows;
	JDIMENSION      undef_row;

	/* debugging check */
	if(end_row > ptr->rows_in_array || num_rows > ptr->maxaccess || ptr->mem_buffer == NULL)
		ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);

	/* Make the desired part of the virtual array accessible */
	if(start_row < ptr->cur_start_row || end_row > ptr->cur_start_row + ptr->rows_in_mem)
	{
		if(!ptr->b_s_open)
			ERREXIT(cinfo, JERR_VIRTUAL_BUG);
		/* Flush old buffer contents if necessary */
		if(ptr->dirty)
		{
			do_barray_io(cinfo, ptr, TRUE);
			ptr->dirty = FALSE;
		}
		/* Decide what part of virtual array to access.
		 * Algorithm: if target address > current window, assume forward scan,
		 * load starting at target address.  If target address < current window,
		 * assume backward scan, load so that target area is top of window.
		 * Note that when switching from forward write to forward read, will have
		 * start_row = 0, so the limiting case applies and we load from 0 anyway.
		 */
		if(start_row > ptr->cur_start_row)
		{
			ptr->cur_start_row = start_row;
		}
		else
		{
			/* use long arithmetic here to avoid overflow & unsigned problems */
			long            ltemp;

			ltemp = (long)end_row - (long)ptr->rows_in_mem;
			if(ltemp < 0)
				ltemp = 0;		/* don't fall off front end of file */
			ptr->cur_start_row = (JDIMENSION) ltemp;
		}
		/* Read in the selected part of the array.
		 * During the initial write pass, we will do no actual read
		 * because the selected part is all undefined.
		 */
		do_barray_io(cinfo, ptr, FALSE);
	}
	/* Ensure the accessed part of the array is defined; prezero if needed.
	 * To improve locality of access, we only prezero the part of the array
	 * that the caller is about to access, not the entire in-memory array.
	 */
	if(ptr->first_undef_row < end_row)
	{
		if(ptr->first_undef_row < start_row)
		{
			if(writable)		/* writer skipped over a section of array */
				ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
			undef_row = start_row;	/* but reader is allowed to read ahead */
		}
		else
		{
			undef_row = ptr->first_undef_row;
		}
		if(writable)
			ptr->first_undef_row = end_row;
		if(ptr->pre_zero)
		{
			size_t          bytesperrow = (size_t) ptr->blocksperrow * SIZEOF(JBLOCK);

			undef_row -= ptr->cur_start_row;	/* make indexes relative to buffer */
			end_row -= ptr->cur_start_row;
			while(undef_row < end_row)
			{
				jzero_far((void FAR *)ptr->mem_buffer[undef_row], bytesperrow);
				undef_row++;
			}
		}
		else
		{
			if(!writable)		/* reader looking at undefined data */
				ERREXIT(cinfo, JERR_BAD_VIRTUAL_ACCESS);
		}
	}
	/* Flag the buffer dirty if caller will write in it */
	if(writable)
		ptr->dirty = TRUE;
	/* Return address of proper part of the buffer */
	return ptr->mem_buffer + (start_row - ptr->cur_start_row);
}


/*
 * Release all objects belonging to a specified pool.
 */

METHODDEF void free_pool(j_common_ptr cinfo, int pool_id)
{
	my_mem_ptr      mem = (my_mem_ptr) cinfo->mem;
	small_pool_ptr  shdr_ptr;
	large_pool_ptr  lhdr_ptr;
	size_t          space_freed;

	if(pool_id < 0 || pool_id >= JPOOL_NUMPOOLS)
		ERREXIT1(cinfo, JERR_BAD_POOL_ID, pool_id);	/* safety check */

#ifdef MEM_STATS
	if(cinfo->err->trace_level > 1)
		print_mem_stats(cinfo, pool_id);	/* print pool's memory usage statistics */
#endif

	/* If freeing IMAGE pool, close any virtual arrays first */
	if(pool_id == JPOOL_IMAGE)
	{
		jvirt_sarray_ptr sptr;
		jvirt_barray_ptr bptr;

		for(sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next)
		{
			if(sptr->b_s_open)
			{					/* there may be no backing store */
				sptr->b_s_open = FALSE;	/* prevent recursive close if error */
				(*sptr->b_s_info.close_backing_store) (cinfo, &sptr->b_s_info);
			}
		}
		mem->virt_sarray_list = NULL;
		for(bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next)
		{
			if(bptr->b_s_open)
			{					/* there may be no backing store */
				bptr->b_s_open = FALSE;	/* prevent recursive close if error */
				(*bptr->b_s_info.close_backing_store) (cinfo, &bptr->b_s_info);
			}
		}
		mem->virt_barray_list = NULL;
	}

	/* Release large objects */
	lhdr_ptr = mem->large_list[pool_id];
	mem->large_list[pool_id] = NULL;

	while(lhdr_ptr != NULL)
	{
		large_pool_ptr  next_lhdr_ptr = lhdr_ptr->hdr.next;

		space_freed = lhdr_ptr->hdr.bytes_used + lhdr_ptr->hdr.bytes_left + SIZEOF(large_pool_hdr);
		jpeg_free_large(cinfo, (void FAR *)lhdr_ptr, space_freed);
		mem->total_space_allocated -= space_freed;
		lhdr_ptr = next_lhdr_ptr;
	}

	/* Release small objects */
	shdr_ptr = mem->small_list[pool_id];
	mem->small_list[pool_id] = NULL;

	while(shdr_ptr != NULL)
	{
		small_pool_ptr  next_shdr_ptr = shdr_ptr->hdr.next;

		space_freed = shdr_ptr->hdr.bytes_used + shdr_ptr->hdr.bytes_left + SIZEOF(small_pool_hdr);
		jpeg_free_small(cinfo, (void *)shdr_ptr, space_freed);
		mem->total_space_allocated -= space_freed;
		shdr_ptr = next_shdr_ptr;
	}
}


/*
 * Close up shop entirely.
 * Note that this cannot be called unless cinfo->mem is non-NULL.
 */

METHODDEF void self_destruct(j_common_ptr cinfo)
{
	int             pool;

	/* Close all backing store, release all memory.
	 * Releasing pools in reverse order might help avoid fragmentation
	 * with some (brain-damaged) malloc libraries.
	 */
	for(pool = JPOOL_NUMPOOLS - 1; pool >= JPOOL_PERMANENT; pool--)
	{
		free_pool(cinfo, pool);
	}

	/* Release the memory manager control block too. */
	jpeg_free_small(cinfo, (void *)cinfo->mem, SIZEOF(my_memory_mgr));
	cinfo->mem = NULL;			/* ensures I will be called only once */

	jpeg_mem_term(cinfo);		/* system-dependent cleanup */
}


/*
 * Memory manager initialization.
 * When this is called, only the error manager pointer is valid in cinfo!
 */

GLOBAL void jinit_memory_mgr(j_common_ptr cinfo)
{
	my_mem_ptr      mem;
	long            max_to_use;
	int             pool;
	size_t          test_mac;

	cinfo->mem = NULL;			/* for safety if init fails */

	/* Check for configuration errors.
	 * SIZEOF(ALIGN_TYPE) should be a power of 2; otherwise, it probably
	 * doesn't reflect any real hardware alignment requirement.
	 * The test is a little tricky: for X>0, X and X-1 have no one-bits
	 * in common if and only if X is a power of 2, ie has only one one-bit.
	 * Some compilers may give an "unreachable code" warning here; ignore it.
	 */
	if((SIZEOF(ALIGN_TYPE) & (SIZEOF(ALIGN_TYPE) - 1)) != 0)
		ERREXIT(cinfo, JERR_BAD_ALIGN_TYPE);
	/* MAX_ALLOC_CHUNK must be representable as type size_t, and must be
	 * a multiple of SIZEOF(ALIGN_TYPE).
	 * Again, an "unreachable code" warning may be ignored here.
	 * But a "constant too large" warning means you need to fix MAX_ALLOC_CHUNK.
	 */
	test_mac = (size_t) MAX_ALLOC_CHUNK;
	if((long)test_mac != MAX_ALLOC_CHUNK || (MAX_ALLOC_CHUNK % SIZEOF(ALIGN_TYPE)) != 0)
		ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);

	max_to_use = jpeg_mem_init(cinfo);	/* system-dependent initialization */

	/* Attempt to allocate memory manager's control block */
	mem = (my_mem_ptr) jpeg_get_small(cinfo, SIZEOF(my_memory_mgr));

	if(mem == NULL)
	{
		jpeg_mem_term(cinfo);	/* system-dependent cleanup */
		ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 0);
	}

	/* OK, fill in the method pointers */
	mem->pub.alloc_small = alloc_small;
	mem->pub.alloc_large = alloc_large;
	mem->pub.alloc_sarray = alloc_sarray;
	mem->pub.alloc_barray = alloc_barray;
	mem->pub.request_virt_sarray = request_virt_sarray;
	mem->pub.request_virt_barray = request_virt_barray;
	mem->pub.realize_virt_arrays = realize_virt_arrays;
	mem->pub.access_virt_sarray = access_virt_sarray;
	mem->pub.access_virt_barray = access_virt_barray;
	mem->pub.free_pool = free_pool;
	mem->pub.self_destruct = self_destruct;

	/* Initialize working state */
	mem->pub.max_memory_to_use = max_to_use;

	for(pool = JPOOL_NUMPOOLS - 1; pool >= JPOOL_PERMANENT; pool--)
	{
		mem->small_list[pool] = NULL;
		mem->large_list[pool] = NULL;
	}
	mem->virt_sarray_list = NULL;
	mem->virt_barray_list = NULL;

	mem->total_space_allocated = SIZEOF(my_memory_mgr);

	/* Declare ourselves open for business */
	cinfo->mem = &mem->pub;

	/* Check for an environment variable JPEGMEM; if found, override the
	 * default max_memory setting from jpeg_mem_init.  Note that the
	 * surrounding application may again override this value.
	 * If your system doesn't support getenv(), define NO_GETENV to disable
	 * this feature.
	 */
#ifndef NO_GETENV
	{
		char           *memenv;

		if((memenv = getenv("JPEGMEM")) != NULL)
		{
			char            ch = 'x';

			if(sscanf(memenv, "%ld%c", &max_to_use, &ch) > 0)
			{
				if(ch == 'm' || ch == 'M')
					max_to_use *= 1000L;
				mem->pub.max_memory_to_use = max_to_use * 1000L;
			}
		}
	}
#endif

}
